Trimming mechanism for form grinders



March 11, 1958 s. G. BRADY TRIMMING MECHANISM FOR FORM GRINDERS s Sheets-Sheet 1 Filed Jan. l6, 195s INVENTOR.

SAMUEL s. BRADY ATTORNEYS S. G. BRADY TRIMMING MECHANISM FOR FORM GRINDERS 3 Sheets-Sheet 2 Filed Jan. 16, 1953 INVENTOR.

SAMUEL s. BRADY ATTORNEYS March 11 1958 s. G. BRADY I TRIMMING MECHANISM FOR FORM GRINDERS 3 Sheets-Shet 3 Filed Jan. 16, 1953 m m w m SAMUEL G. BRADY 9min WAM ATTOR N EYS United States Patent TRIMMING MECHANISM FOR FORM GRINDERS Samuel G. Brady, Royal Oak, Mich., assignor to The Gear Grinding Machine Company, Detroit, Mich, a corporation of Michigan Application January 16, 1953, Serial No. 331,535

7 Claims. (Cl. 125-41) The invention relates to trimming mechanisms for form grinding machines and more particularly to that type in which a diamond cutter carried by an actuating mechanism trims a grinder wheel to a predetermined crosssectional contour. If the cutter isin the form of a point it will soon be worn off so that it is customary to provide the diamond with a more extended cutting edge. However, with such extended edge it is more difiicult to obtain precision in the form of trimmed contour on account of varying angular movements of the carrying mechanism. Also, all points in the cutting edge may not wear equally, which again is the cause of inaccuracy.

It is the object of the invention to obtain a construction of trimming mechanism in which extension. of the cutting edge of the diamond will not affect the accuracy of the contour trimmed. It is a further object to distribute the wear along this cutting edge so as to maintain the form thereof.

With these objects in view the invention consists, first, in a trimming mechanism in which the trimming edge of the cutter is of arcuate form and is concentric with a point in the carrier mechanism which traverses the exact contour desired. The invention further consists in means operating during the trimming of the contour for oscillating the cutter about the center of its arcuate cutting edge to distribute the wear thereon and to maintain the form.

The invention further consists in more specific features of the construction as hereinafter set forth.

In the drawings:

Fig. 1 is a front elevation of the trimming mechanism which, as specifically .shown, is of the pantograph type; Fig. 2 is an end elevation thereof partly in section;

Fig. 3 is a plan view of a portion of the mechanism illustrating partly in section the means for imparting oscillatory movement to the cutter;

Fig. 4 is an elevation of the oscillating means shown more or less diagrammatically;

Fig. 5 is an elevation of a portion of the mechanism viewed from the left in Fig. 2;

Fig. 6 is an enlarged elevation of a portion of Fig. 1 showing the diamond cutter and its holder.

While the characteristic features of my improvement may be applicable to various types of trimming mechanisms, I have specifically illustrated the same as applied to the pantograph type. As shown in Fig. l, A is a pantograph which is of usual general construction comprising an arm A anchored at one end through a pivot B to a stationary support, an arm A pivotally connected at B to the free end of the arm A, an arm A parallel to the arm A pivotally attached at one end at B to the arm A and thelink A parallel to the arm A and pivotallyconnected at its opposite'ends to the arms A and A at B and B, respectively. This constitutes a parallelogram frame in which any contour traced by a point in the outer end of the arm A will be reproduced on smaller scale by a point in the axis of the pivot connecting the arm A with the link A It is to be understood that the point in the arm A must accurately align r 2,826,188 C Patented'Mar. 11, 1958 with the axes of the pivots respectively connecting the arm A with the link A and the arm A with the stationary support. Inasmuch, however, as the cutting edge of the diamond cutter is not a point but a line it cannot be located in the axis of the pivot but may be arcuate and concentric with this axis. Thus, as shown in Fig. 2, the pivot B connecting the arm A with the link A is a pin which at one end is connected with an outwardly extending trimmer arm C and a diamond holder D is adjustably connected to the outer end of the arm. This holder is a cylindrical member engaging a corresponding socket in the member C and extending transversely thereof. The diamond E is set in the end of the holder D and is fashioned to have an arcuate cutting edge E. This by adjustment of the holder in its socket may be placed so that the center of the arc is in the axis of the pivot B. The contact member F at the outer end of the arm A which traces the pattern is preferably a roller, the radius of which is in the same ratio to the radius of the arcuate cutting edge as the ratio in degree of reduction of the trimmed contour from that of the pattern.

To impart an oscillatory movement to the cutter there is provided an oscillating mechanism which preferably is of the following construction: G is a frame in which is journaled a shaft H having mounted thereon and fixed thereto a gear wheel I. J is an internal gear wheel surrounding the gear wheel I and sleeved to independently rotate upon the shaft H. K is a pinion intermediate and in mesh with the gear wheels I and J, which pinion is mounted on a carrier L, also sleeved on the shaft H. M is a motor or other means for rotating a crank M. This crank is connected by a crank pin M to a rod M the opposite end of which is pivotally connected at J to the internal gear wheel I so that in the rotation of the crank an oscillation will be imparted to said gear wheel. By adjusting the pin M radially of the crank M the amplitude of the oscillation may be varied. If the pinion K is held stationary, the oscillation of the gear wheel J will be transmitted to the gear wheel I, which will impart a similar oscillation to the shaft H. A pulley H on the shaft is connected by a belt transmission N to a pulley N which is concentric with the axis of the pivot B connecting the arm A with its stationary anchor. A second pulley N coaxial with and connected to the pulley N is connected by a belt N with a pulley N concentric with the axis of the pivot B which connects the arm A with the link A". A coaxial pulley N coupled with the pulley N is connected through a belt N with a pulley N secured to the pivot pin B. Thus through this transmission the oscillation of the shaft H is transmitted to the pivot pin B and the trimmer arm C connected thereto. The latter will impart oscillation to the holder D and diamond E, the arcuate cutting edge E of which is concentric with the axis of the pivot pin B. Obviously this transmission will not in any way interfere with freedom of movement of the pantograph inasmuch as the pulleys of the transmission are coaxial with the pantograph pivots.

The construction as thus far described is operable to trim a grinder wheel, such as O, which is placed in operative relation thereto provided that the angular change in contour is not too great. Usually in gear grinding machines separate trimming cutters are used for trimming the portions of the grinder which correspondto opposite sides of a gear tooth and therefore the change in angle of contour is not very great. If, however, the same cutter is used for trimming the portions of the grinder wheel corresponding to bothsides of the tooth a much greater change in angle is required. This would be greater than the angle of the arcuate cutting edge of the diamond. I have, therefore, provided means independent of the means for oscillating the cutter for 'lation of theinternal gear wheel I.

periodically adjusting thelatter through a greater angle around the center of the are. This means comprises a rock-arm L on the carrier L through which said carrier may be revolved about its axis through a predetermined angle. Such movement will, through the pinion K, impart a'rotation to the gear wheel I, shaft H and pulley H which is independent of that transmitted thereto by oscil- The belt and pulley transmission previously described will transmit this additional rotation to the pivot pin B, trimmer arm C, holder D, and diamond E. It will, therefore, be understood that in one position of the rock arm L the oscillating arcuate trimming edge will occupy a segment suitable for trimming one side of the grinder wheel, and when said arm is moved to another position, the oscillation will be in another segment suitable for trimming the opposite side of the wheel.

More in detail and as shown in Fig. l, the pattern P around which the contact roller F is moved has one portion P of its contour corresponding to one side of the trimmed grinder and another portion P corresponding to the opposite side. intermediate these two portions is a connecting portion P If the contact wheel is passed continuously around the pattern from the portion P through the portion P to the portion P angular adjustment of the cutter must be made at an intermediate point. Automatic means for accomplishing such adjustment is 'diagrammaticaly illustrated in Fig. 4 in which Q is a cylinder containing a piston Q which is connected by a rod Q to the arm L. R is a valve controlling a supply of hydraulic fluid and R and R are conduits connecting the valve to opposite ends of the cylinder Q. In one position of the valve R, fluid is transmitted through the conduit R to the cylinder Q so as to hold the piston at the right end of said cylinder. On the other hand, when the valve is shifted, fluid transmitted through the conduit R will move the piston to the opposite end of said cylinder.

Such movements will correspondingly adjust the rockarm L and shift the position of the oscillating cutter. The valve R may, if desired, be automatically operated by movement of the pantograph and as shown this is accomplished by the following: S is a solenoid or other electro-magnetic means for actuating the plunger of the alve R in one direction, when energized said plunger being biased by spring means to automatically return when the solenoid is deenergized. T is an electric switch for controlling the solenoid S, and T is a plunger which in one position thereof closes such switch, and in all other positions opens the circuit. T he switch is mounted on the stationary anchor for the pantograph with the plunger T extending outward therefrom. T is a pad mounted on the link A which extends into the path of the plunger T and in certain movements of the link actuates the plunger in one direction against the pressure of a spring which biases it to move in the opposite direction. The position ofthe parts is such that as long as the pantograph has its contact roller F in engagement with the portion P of the pattern, the pad T will hold the plunger T in a position to open the switch and deenergize the solenoid. On the other hand, when the roller F is moved beyond the center of the portion P of the pattern the pad T will be removed sufiiciently from the path of the plunger to permit the closing of the switch. Thus, it will be understood that the switch will be closed during passage of the roller F from the portion P to the portion P of the pattern and will be opened by the passing of said roller from the portion P to the portion P. Such automatic mechanism, however, is not necessary and if desired the operator in moving the contact roller F from the portion P of the pattern to the portion P may manually operate the valve R to effect the shifting of the oscillating cutter into another segment.

A more detailed description of the mechanism is not important, but as shown in Fig. 2, the arm A of the pantograph is bifurcated at its opposite end, the bifurcation at one end embracing a stationary bearing U to which the pantograph is attached by the pin B and also embracing the link A The opposite bifurcation embraces the arm A to which it is connected by a pivot pin B What I claim as my invention is:

I. In a trimming mechanism for rotary form grinders, in which a tool of hardness on the order of the diamond is contacted with the periphery of the rotary grinder wheel and advanced through a path corresponding to the desired cross sectional contour of said wheel, the combination of a cutter carried by said mechanism having an arcuate cutting edge of small radius, and means operating during the trimming movement of said cutter through said path in a plane transverse to the axis through the center of the are for continuously rapidly oscillating said cutter through a limited angle about said center of the arc while it is ad vanced.

2. The construction as in claim 1 in which said trimming mechanism is a pantograph, and the center of said arcuate cutting edge is the axis of one of the pivot pins of said pantograph.

3. The construction as in claim 1 provided with adjustment means for varying the amplitude of the angular con tinuous oscillation.

4. The construction as in claim 1 having means for angularly adjusting said cutter to continuously and rapidly oscillate within a different segment about the center of said arcuate cutting edge.

5. The construction as in claim 4 in which the mechanism for said oscillating means and angular adjustment means comprises a sun gear, a coaxial surrounding internal gear, a pinion intermediate and enmeshed with said gears, a carrier for said pinion angularly adjustable concentric with the common axis of said gears, a belt and pulley transmission from one of the gears to said cutter, means for oscillating the other of said gears, and means for angularly adjusting said pinion about the common axis of said gears to impart an additional angular movement to said belt and pulley transmission and shift the oscillation into a different segment.

6. A trimming mechanism for rotary form grinders comprising a rotary grinder wheel, a cutter having an arcuate edge for engaging said rotary grinder wheel, a carrier for said cutter, means for moving said carrier to feed the arcuate edge of said cutter across the edge of said rotary grinder wheel along a predetermined path to thereby trim said edge to a predetermined cross sectional contour and means operable during said feeding move ment of the carrier for oscillating said arcuate edge about the center of its .arc.

7. A trimming mechanism according to claim 6 in which said arcuate edge is on a diamond cutter.

References Cited in the file of this patent UNITED STATES PATENTS 79,351 'Hine June 30, 1868 80,338 Daniels July 28, 1868 735,605 Smith Aug. 4, 1903 1,392,528 Schmick Oct. 4, 1921 2,233,398 Carlin Mar. 4, 1941 2,358,393 Greve Sept. 19, 1944 2,469,844 Porter May 10, 1949 2,601,810 James July 1, 1949 FOREIGN PATENTS 623,393 Great Britain May 17, 1949 

